1. Field of the Invention
The present invention relates to a vane pump for compressing or decompressing fluid.
2. Description of Related Art
A vane pump having a rotor rotating in an eccentric relation with respect to an inner bore of a casing is known hitherto. The vane pump has vanes disposed in grooves formed in the rotor to extend in the axial direction. The vanes move in the radial direction according to rotation of the rotor so that radial ends of the vanes slidably contact the inner bore of the casing. An axial length of the vane is made a little smaller than an axial length of the groove to allow its smooth movement in the groove. In other words, small gaps are formed between the vane and casing. Accordingly, the vane moves also in the axial direction according to rotation of the rotor and tends to hit the casing, generating hitting noises.
JP-A-6-147156 proposes a vane pump that has resilient rings for pushing the vanes in the radial direction against the inner bore of the casing. By pushing the vanes against the inner bore, movement of the vanes in the axial direction is also suppressed. In the proposed vane pump, however, it is necessary to provide the resilient rings that make the vane pump complex and expensive.